CDTV no display issue

[jrtolson]

when i get time over the weekend im going strip the cdtv again to ty and dissasemble the cdrom, i could not do that the first time as the fron two screws holding the cd drive and electronics in will no budge for love no money.. so i will have to learn the force and become a jedi to strip it completly without chewing up the screws, but i reckon the lens is probabily dirty..

as for the sound, i downloaded the schematics for the audio section and following the pins from paula the sound goes through one opamp chip (left one in pic) twice (each chip has 4 amps in them) then it and the cd audio goes through the second op amp chip(the right one in pic) once (2 not used) then a tiny cap, a ressistor or 2 then phono jack out. it also looks like the  front panel audio also comes out straight after the second opamp..

so my next action is hook the cdtv up to an amp (my main stereo) and find the channel at fault, also test the fron audio jack to see if thats at fault too, if so it will illiminate the caps/ressistors after opamp 2...

reading some other forums, it could be a power issue, when connect to my logitech active amp i get random pops and load squrks, which could be overvoltage spikes feeding the opamps, so that would be another thing to check maybe?

if the LF347N is at fault, i will then get some more and replace them (seen them for 50 pence each on a website lol)

one question i have tho is if the second opamp only uses 2 amp in it can i just flip the chip over? i know then the vcc +/- will be reversed but apart from that all the other pins are the same? but i don't know if the chip would work in a reverse polarity setup? im no expert lol, just an idiot with an soldering iron :-)

any advise will be greatly appreciated.. thank you :-)

[Tension]

you afraid cdtv be a broken. thankyov

[arttu80]

I'm very glad my little hack was of help to you. It's always a good thing to have one more Amiga machine resurrected. I must say, that you were a man on a mission with this one!

As for question about jumpering some Sync -signals, I just studied schematics and jumpered only ones wich lines were interrupted on Video Module connector (CN10). But as I see it, you were succesful with your soldering iron. Hope you can solve other problems with your machine. As for sound problem I suspect old caps. And you should measure voltages on your CD -drive connector just to be sure. Just download Service Manual from this fine gentleman --->

http://www.bombjack.org/commodore/amiga/amiga-commodore/CDTV_Service%20Manual_400403-01_%281991_May%29.pdf

and you will succeed!

[jrtolson]

another update,

after a complete dissasembly of the CDTV, (which included drilling out stuborn screws keeping the entire cd rom assembly in place) i cleaned the cd laser manually and reassembled also during reassembly i checked all caps on the sound stage of the pcb (mainly arround the dc power in area) i found that some of the caps legs had become squashed down causing the legs to become extremely intimate with each other so with a small tool i gently persuaded them away from each other, as i figured the popping and poor sound quality could be because there is a short somewhere?

just a word about the cd rom dissasembly, it is very awkward and time consuming and extremely fiddley, the cd lens cleaning mount retaining spring pops away when the top plate is removed and is extremely tedious and annoying to put back in (took me a while lol)

Good news is that sound now seems to be fixed, must have been the capacitor legs shorting

the mouse port mod seems to be broke now, must be because i flipped it back and routed the ribbon cable through the underside of the motherboard ill have to sort that..

the bad news is that the cd rom drive is still not working right :-(

the CDTV seems to have trouble mounting a cd, it seems to work best when booted from cold, for e.g i know if i power it up from cold putting a cd in will either work first time or after a few attempts, but after say 10/15 minutes i eject a cd and put another in it will either take 500 ejects/resets to recognise another or the same disc? or i give up out of fustration lol. The wierd thing is tho once it recognises a disc and mounts it, it will work fine until i eject it.. whether it be after a few minutes or a full day?


above is the laser lens prior to cleaning

above is the underside of the cd drive pcb note some of the ic's look like they have melted a little?

when a disc is inserted the disc spins slowly, the light comes on and i can hear the laser head movind to the center of the disc to read, it then most of the time just stops (light goes out)and does nothing, i then press the eject button (not fully) to make it think i have reinserted the disc, i keep doing this until after the innitial read the disc will start spinning full speed (thats when i know it has worked)

interestingly tho even tho the discs refuse to mount the screen does not go red (indicating a non supported disc) i guess it fails before it gets to that stage i dunno...

well if anyone has any more suggestions i would be very greatfull, i have tried pushing the caddy down, but that makes no difference..

oh and thanks arttu80 that service manual will come in handy :-)

one last thing, when i took the cd drive apart, i spent a while trying  to figure out how the drive actually recognises a disc has been  inserted? there is no pressure switch, latch, sensors anywhere, just the  mechanical mechanism, wires only go to the laser and motor, nothing  else? i figure maybe some sort of electrical contact on the caddy? but  nope.. my only guess is magnetic induction from the center cd mount (as  it magnetically connects to the small disc that is in the caddy lid  cplamping the cd in place), anyone have any insight on that?